Epidural anesthesia is a form of central neuraxial block that allows for variable and prolonged inhibition of neuronal signaling, including autonomic, sensory, and motor transmission. This technique is used both alone and in conjunction with general anesthesia for a wide array of indications such as surgery, postoperative pain control, obstetrics, and chronic pain conditions. Significant neurologic complications as a result of epidural anesthesia have been reported; however, these appear rare. Neuraxial blockade can be safely used in many patients, including patients with preexisting neurologic conditions like myasthenia gravis or multiple sclerosis, though risk benefit should be weighed in each patient.
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• Epidural anesthesia is a type of neuraxial blockade that is indicated for a wide variety of surgical procedures and pain management.
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• Epidural anesthesia can be safely used in most patient populations, including those with preexisting neurologic conditions such as multiple sclerosis and myasthenia gravis.
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• NSAID or aspirin use is not a contraindication to epidural anesthesia for low and moderate risk procedures.
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• Neurologic complications of epidural anesthesia can be severe; however, they appear rare, occurring in fewer than 1 in 1100 subjects.
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• Epidural anesthesia procedures are mostly used in patients undergoing labor and delivery, and the frequency of neurologic complications is about the same in pregnant women compared to nonpregnant patients, though of greater severity in the nonpregnant group.
Historical note and terminology
The use of epidural anesthesia has a longstanding history in medical literature, with the first described attempts dating back to 1901. At that time, French physicians Jean-Anthanase Sicard and Fernand Cathelin independently attempted the use of cocaine injections into the sacral hiatus for the treatment of sciatic nerve pain and operative pain management, respectively (81). Despite these early attempts, it would be another 3 decades before this technique gained widespread use and popularity. In 1931 the Romanian obstetrician Dr. Aburel pioneered the use of a fixed catheter to provide continuous epidural analgesia to parturient patients and in 1933 the Italian surgeon Dr. Dogliotti utilized single dose lumbar epidural injections for abdominal surgery (30). In the following decades advances in needle and catheter manufacturing as well as in procedural techniques resulted in widespread use and acceptance of epidural anesthesia. Although case reports of permanent neurologic disability resulting from the procedure emerged in this timeframe, subsequent large-scale studies, most recently from France and Sweden, have shown these to be uncommon (Dahlgren et al 1995; 04). Today epidural anesthesia is now an increasingly utilized modality for both perioperative and chronic pain management. In recent years imaging modalities, particularly ultrasound, have become more commonly used adjuncts in the administration of epidural anesthesia (59).
As the name suggests, epidural anesthesia takes advantage of the space between the spinal cord, its membranous coverings, and the spinal canal. The human spinal cord extends from the medulla to its terminal ending at the conus medullaris, around the level of L1 in most adults. From this point the lower spinal nerves converge to form the cauda equina and travel more distally before exiting the intervertebral foramen. Like brain parenchyma, the spinal cord is protected by 3 distinct dural layers, or meninges, the pia, arachnoid, and dura maters. The highly vascular pia mater lies directly adjacent to the spinal cord and both are surrounded in CSF, before being encompassed by the avascular structure of the arachnoid mater. Finally, the membranous layer of the dura mater separates the spinal cord and more interior membranes from the vertebral canal. The area between the dura mater and the vertebral canal makes up the epidural space and is bounded by ligamentous structures, ie, the posterior longitudinal ligament and ligmentum flavum, and bony structure of the vertebral pedicles and intervertebral foramen. Injection into this space allows for the application of local anesthetics and anesthetics, such as opioid narcotics, to spinal nerve roots with minimal risk of structural damage to the spinal cord or direct injection into the CSF.